The following invention relates to a lobed chuck for holding a saw blade during a regrinding operation.
Circular saw blades such as those used in sawmills for cutting boards from logs typically must be sharpened or reground on a regular basis. The regrinding of the saw teeth requires both a side regrinding and a top regrinding operation. The regrinding of the top of the saw tooth is especially critical because the teeth must be reground to precise tolerances with respect to the diameter of the shaft which holds the circular saw while in ordinary use.
Many such saw blades are adapted to be fitted on splined arbors, and as such, have a circular inner diameter aperture and an outer diameter aperture which represents the inner diameter plus twice the radius of a plurality of semicircular scallops which are cut in order to fit the saw onto the splines of the arbor. With these saws, the critical dimension which must be maintained for efficient operation is the distance between the tip of the saw teeth, i.e., the outermost diameter of the saw blade, and the outer diameter of the saw's center mounting aperture. This is because in normal operation the scallops which engage the splines of the arbor will experience wear which may be uneven. This in turn will cause the saw blade to engage the wood in an uneven manner.
As an example, saws are dimensioned for a particular "chip load." The chip load is the amount of wood that the saw will rake during each revolution. When the saw's mounting aperture is not true with respect to the outer diameter of the blade, the chip load may be greater on one side of the saw than the other. In its worst case this can cause catastrophic failure of the blade. It is therefore critically important to maintain precise tolerances between the outer diameter of the saw blade, i.e., the tip of the teeth and the outer diameter of the scalloped mounting aperture.
In the past, saw blades have been reground in machines that hold the saw blade steady on a chuck and which rotate it while grinders grind the top of the saw teeth. Such chucks are typically frustum-shaped members which snugly engage the inner diameter of the mounting aperture so that the regrinding of the teeth to the tolerance desired is done with reference to the inner diameter. As mentioned above, however, the wear during normal use is experienced along the outer diameters of the scallops of the saw blade's mounting aperture and regrinding the saw with reference to the inner diameter will not assure concentricity of the mounting aperture with respect to the splined arbor.